CVE-2026-55603

HIGHPre-NVD 7.57.5—
EchelonGraph scoreMEDIUM confidence

This high-severity CVE scores 7.5 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.3%, top 80% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, secondary
Trending — 3 sources updated this weekElevated
7.5EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 7.5Exploit: Elevated riskExposed: 0

A fix is available — apply it.

http-proxy-middleware is node.js http-proxy middleware. From 3.0.4 until 3.0.7 and 4.1.1, fixRequestBody() is the library's documented helper for re-emitting a request body that was already consumed by a body parser. When the outgoing Content-Type is multipart/form-data, it rebuilds the body with handlerFormDataBodyData(), which interpolates each req.body key and value directly into the multipart wire format without neutralizing CR/LF. A \r\n inside a value (or key) lets an attacker close the current part and inject an entirely new form part. Because the proxy's own body parser saw a single opaque value, any gateway-side policy or validation performed on req.body is evaluated against a different set of fields than the upstream backend ultimately parses a request/parameter desynchronization across the trust boundary. This vulnerability is fixed in 3.0.7 and 4.1.1.

CVSS v3
7.5
EG Score
7.5(medium)
EG Risk
50(Track)
EG Risk 50/100SSVC: Track

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity75% × 45%
Exploitation40% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
21%
KEV
Not listed

Published

June 18, 2026

Last Modified

June 24, 2026

Advisory Details (1)

Auto-updated Jun 22, 2026
🔬 Proof of concept available. Patch available. Sources: github.
github Patch Available🟡 PoC Available

multipart/form-data field injection via unescaped CRLF in `fixRequestBody` · Advisory · chimurai/http-proxy-middleware · GitHub

https://github.com/chimurai/http-proxy-middleware/security/advisories/GHSA-gcq2-9pq2-cxqm

Vendor Advisories for CVE-2026-55603(3)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Patch Availability(2)

Vendor / EcosystemFixed in / PatchReleasedSource
redhatmta/mta-ui-rhel9:17851690132026-08-04redhat
redhatrhtas/rhtas-console-ui-rhel9:17841058942026-07-20redhat

Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.

Affected Packages

(1 across 1 ecosystem)
npm(1)
PackageVulnerable rangeFixed inDependents
http-proxy-middleware—4.1.1—

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 17× in last 7d / 99× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

Showing the most recent 100 of 152 total refreshes for this CVE.

  1. 2026-08-26 14:46 UTCEPSS rescore
  2. 2026-08-25 13:49 UTCEPSS rescore
  3. 2026-08-24 22:21 UTCEG score recompute
  4. 2026-08-24 22:21 UTCVendor advisory
  5. 2026-08-24 05:13 UTCVendor advisory
  6. 2026-08-23 15:16 UTCVendor advisory
  7. 2026-08-23 03:45 UTCEG score recompute
  8. 2026-08-23 03:45 UTCVendor advisory
  9. 2026-08-23 00:19 UTCEPSS rescore
  10. 2026-08-21 23:49 UTCEPSS rescore
  11. 2026-08-21 18:53 UTCVendor advisory
  12. 2026-08-21 07:22 UTCEG score recompute
  13. 2026-08-21 07:22 UTCVendor advisory
  14. 2026-08-20 22:55 UTCEPSS rescore
  15. 2026-08-20 19:41 UTCVendor advisory
  16. 2026-08-20 08:11 UTCEG score recompute
  17. 2026-08-20 08:11 UTCVendor advisory
  18. 2026-08-19 17:04 UTCEPSS rescore
  19. 2026-08-19 08:01 UTCEG score recompute
  20. 2026-08-19 08:01 UTCVendor advisory
  21. 2026-08-18 13:48 UTCEPSS rescore
  22. 2026-08-17 13:47 UTCEPSS rescore
  23. 2026-08-17 08:17 UTCVendor advisory
  24. 2026-08-16 20:47 UTCEG score recompute
  25. 2026-08-16 20:47 UTCVendor advisory
Show 75 more
  1. 2026-08-16 14:56 UTCEPSS rescore
  2. 2026-08-16 08:43 UTCEG score recompute
  3. 2026-08-16 08:43 UTCVendor advisory
  4. 2026-08-16 02:14 UTCEPSS rescore
  5. 2026-08-15 21:12 UTCVendor advisory
  6. 2026-08-15 09:07 UTCEG score recompute
  7. 2026-08-15 09:07 UTCVendor advisory
  8. 2026-08-15 01:30 UTCEPSS rescore
  9. 2026-08-14 20:55 UTCVendor advisory
  10. 2026-08-14 09:24 UTCEG score recompute
  11. 2026-08-14 09:24 UTCVendor advisory
  12. 2026-08-13 22:00 UTCEPSS rescore
  13. 2026-08-13 21:54 UTCVendor advisory
  14. 2026-08-13 10:23 UTCVendor advisory
  15. 2026-08-12 22:52 UTCEG score recompute
  16. 2026-08-12 22:52 UTCVendor advisory
  17. 2026-08-12 13:51 UTCEPSS rescore
  18. 2026-08-12 11:22 UTCVendor advisory
  19. 2026-08-11 23:51 UTCEG score recompute
  20. 2026-08-11 23:51 UTCVendor advisory
  21. 2026-08-11 12:20 UTCVendor advisory
  22. 2026-08-11 00:47 UTCEG score recompute
  23. 2026-08-11 00:47 UTCVendor advisory
  24. 2026-08-11 00:00 UTCEPSS rescore
  25. 2026-08-10 13:16 UTCVendor advisory
  26. 2026-08-10 01:46 UTCVendor advisory
  27. 2026-08-09 14:15 UTCEG score recompute
  28. 2026-08-09 14:15 UTCVendor advisory
  29. 2026-08-09 13:46 UTCEPSS rescore
  30. 2026-08-09 02:45 UTCEG score recompute
  31. 2026-08-09 02:45 UTCVendor advisory
  32. 2026-08-08 16:37 UTCEPSS rescore
  33. 2026-08-08 15:15 UTCVendor advisory
  34. 2026-08-08 03:44 UTCEG score recompute
  35. 2026-08-08 03:44 UTCVendor advisory
  36. 2026-08-07 16:13 UTCVendor advisory
  37. 2026-08-07 04:42 UTCVendor advisory
  38. 2026-08-06 17:11 UTCEG score recompute
  39. 2026-08-06 17:11 UTCVendor advisory
  40. 2026-08-06 13:47 UTCEPSS rescore
  41. 2026-08-06 05:40 UTCEG score recompute
  42. 2026-08-06 05:40 UTCVendor advisory
  43. 2026-08-05 19:17 UTCEPSS rescore
  44. 2026-08-05 18:09 UTCVendor advisory
  45. 2026-08-05 02:54 UTCVendor advisory
  46. 2026-08-04 15:24 UTCEG score recompute
  47. 2026-08-04 15:24 UTCVendor advisory
  48. 2026-08-04 15:10 UTCEPSS rescore
  49. 2026-08-04 10:39 UTCEPSS rescore
  50. 2026-08-03 20:16 UTCEG score recompute
  51. 2026-08-03 20:16 UTCVendor advisory
  52. 2026-08-03 10:36 UTCEPSS rescore
  53. 2026-08-03 08:45 UTCVendor advisory
  54. 2026-08-02 19:43 UTCVendor advisory
  55. 2026-08-02 08:12 UTCEG score recompute
  56. 2026-08-02 08:12 UTCVendor advisory
  57. 2026-08-02 02:27 UTCEPSS rescore
  58. 2026-08-01 20:41 UTCVendor advisory
  59. 2026-08-01 09:09 UTCEG score recompute
  60. 2026-08-01 09:09 UTCVendor advisory
  61. 2026-08-01 04:16 UTCEPSS rescore
  62. 2026-07-31 21:38 UTCVendor advisory
  63. 2026-07-31 10:07 UTCVendor advisory
  64. 2026-07-30 22:33 UTCEG score recompute
  65. 2026-07-30 22:33 UTCVendor advisory
  66. 2026-07-30 16:28 UTCEPSS rescore
  67. 2026-07-30 03:13 UTCEG score recompute
  68. 2026-07-30 03:13 UTCVendor advisory
  69. 2026-07-30 01:30 UTCEPSS rescore
  70. 2026-07-29 13:27 UTCVendor advisory
  71. 2026-07-29 01:48 UTCEG score recompute
  72. 2026-07-29 01:48 UTCVendor advisory
  73. 2026-07-28 15:37 UTCEPSS rescore
  74. 2026-07-28 06:08 UTCVendor advisory
  75. 2026-07-27 18:37 UTCEG score recompute

Frequently asked(5)

What is CVE-2026-55603?
CVE-2026-55603 is a high vulnerability published on June 18, 2026. http-proxy-middleware is node.js http-proxy middleware. From 3.0.4 until 3.0.7 and 4.1.1, fixRequestBody() is the library's documented helper for re-emitting a request body that was already consumed by a body parser. When the outgoing Content-Type is multipart/form-data, it rebuilds the body with…
When was CVE-2026-55603 disclosed?
CVE-2026-55603 was first published in the National Vulnerability Database on June 18, 2026, with the most recent update on June 24, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-55603 actively exploited?
CVE-2026-55603 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0% probability of exploitation in the next 30 days, which ranks it in the top 79.4% of all scored CVEs.
What is the CVSS score of CVE-2026-55603?
CVE-2026-55603 has a CVSS v3 base score of 7.5 (NVD).
How do I remediate CVE-2026-55603?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-55603, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

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